On 07/17/2017 09:23 AM, Gene Heskett wrote:
On Monday 17 July 2017 11:08:19 andy pugh wrote:
On 17 July 2017 at 15:42, Gene Heskett <ghesk...@shentel.net> wrote:
I saw that, and the long pipe gripped in the chuck with the huge
bearing so it all turned. The bearing is nice but $$$$$$ and not
needed if the tube is turned truly round.
I imagine that a suitable bearing could be found that would not be all
that expensive, especially as you could make the tool to suit the
available bearing.
http://www.ebay.com/itm/280920636178 looks like it could work.
And I seem to recall that rifle barrels are very rarely circular.
(though in the case of that rig in the video the real problem would be
the gun carriage trunnions)
In the case of a bolt action hunting rifle, that stuff is on the action,
barrels are generally turned smooth. Any taper is optional, this one
tapers to .82" at the muzzle. The only place where the installed
barrels rotation is important is a flat just wide enough to clear the
claw style extractor when the bolt is closed. Its often filed by hand
after the barrel is screwed in and an impression made in some modeling
clay to mark the boundaries by the bolt, with extractor mounted, being
pushed into the clay. Or a witness mark made on the bottom. It could be
cut with the right sized milling tool. Remove it, file the flat, and
reinstall to the same torque, with a 4 or 5 foot handle on the action
wrench.
One thing I'd like to see some attention paid to, is designing a taper
that doesn't have a natural resonant frequency. But most just turn for
pretty, or hitting a max allowable weight. Such barrels tend to be quite
picky about the load for best accuracy, often found by loading in slowly
increasing charges, and shooting to see the movement on target as the
charge is increased. The most accurate load will generally correspond
to the widest swing of the string on the target because at the peak of
the widest string, the barrel is moving the slowest as it peaks at the
swing point at the instant the bullet leaves the muzzle. At that point,
a small variation in charge or ignition has the least effect on the
impact point. Change the load so its at the mid-point of that vibration,
perhaps a 2% change, and it becomes much more sensitive to a .1% change
in the load because that movement swing is at the highest velocity.
Bug hole guns are a whole science in themselves. So are the shooters who
can make them perform. At my age and eyesight today, I am long past my
peak. So I cheat with ever more powerfull glass sights. I can recall a
shooter on an adjacent bench in 1978, calling my attention to a fly
sitting on the corner of my target, 100 meters out. I moved a few grains
of sand in the bags and said "do you mean that one?" as my rifle spoke.
He said I missed, so we bet a 6 pack and walked out to look at the
target. The bullethole had bloodstained edges. ;-) But that was 39
years ago. And I had a Bud to wash down dinner that evening.
Cheers, Gene Heskett
Gene,
I've seen strips of pop cans used as a buffer (static) between the
chuck jaws and a barrel.
There are also some steady-rests done with hydraulics so that there is
always a dampening
load on the barrel but not binding. Good, fast, cheap: pick any two.
Dave
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